Crystal Load Capacitance Calculator
Calculate effective crystal load and the equal external capacitors needed for an entered target load.
YOUR CALCULATION
Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Combine the two grounded external capacitors in series and add your aggregate equivalent parallel stray capacitance.
CL=C1 C2/(C1+C2)+Cstray; equal external C=2(target CL−Cstray)
Worked example
Two 22 pF capacitors plus 3 pF equivalent stray give effective load 14 pF. A target 18 pF requires equal 30 pF external capacitors under the same model.
Assumptions and input details
Target must exceed equivalent stray. Model does not calculate oscillation startup, drive level, ESR, frequency pulling, PCB parasitics or a particular crystal/device compatibility.
References: Microchip AN849: crystal load capacitance
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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